The present invention disclosed herein relates to a positive electrode active material, and a positive electrode and lithium secondary battery including the same, and more particularly, to a positive electrode active material employing active materials with excellent thermal stability, which have two different types and particle sizes to obtain high volumetric density and thus improve stability, and a positive electrode and lithium secondary battery including the same.
A lithium secondary battery has higher voltage and capacity than a typical nickel cadmium secondary battery. Especially, when a typical lithium transition metal such as LiCoO2, LiNiO2, or LiMn2O4 is used as a positive electrode active material, and graphite or carbon such as carbon fiber is used as a negative electrode active material, a high voltage of more than about 4 V may be generated and concerns about side effects such as electrical short may become less. Therefore, their availabilities as a portable power of a mobile electronic device such as a mobile phone, a notebook PC, and a digital camera are high.
As mobile devices have been continuously lighter and more compact with high performance and various functions and also required to operate under high or low temperature environments, characteristics such as high-level electric capacity, electric discharge/charge, and safety are essential.
Accordingly, a typical lithium battery simply using a LiCoO2 powder of a predetermined form as a positive electrode active material may not provide the above-mentioned battery characteristics. To satisfy the above battery characteristics, various kinds of typical techniques are introduced.
For example, a technique for coating positive electrode active material particles is suggested. However, this technique has difficulty in actual application due to complex manufacturing processes.
As another technique, a technique for improving the packing density of active material particles is suggested. A related art about the above techniques may be disclosed in patent documents below.
Japan patent publication No. 2000-082466 discloses that a lithium cobalt complex oxide has an average particle diameter of about 0.1 μm to about 50 μm and a positive electrode active material has two peaks in a particle distribution.
Korean patent publication No. 2002-0057825 discloses positive electrode active materials mixed with a positive electrode active material having an average particle diameter of about 7 μm to about 25 μm and a positive electrode active material having an average particle diameter of about 2 μm to about 6 μm.
Japan patent publication No. 2004-119218 discloses positive electrode active materials mixed with a positive electrode active material having an average particle diameter of about 7 μm to about 20 m and a positive electrode active material having an average particle diameter, which is about 10% to about 30% of the former.